When a mobile device connected to a wireless GPRS network goes out of coverage, the device typically does not immediately disconnect from the network. Rather, a typical mobile device will queue outgoing data frames for transmission one coverage is re-established. These queued data frames may include user data, network control data (e.g., a GPRS attach request, a Packet Data Protocol (PDP) context request, etc.), or other information.
If the initial network connection is still valid when coverage is re-established, then the queued data frames may be transmitted from the mobile device to the network with no interruption in communication. However, if the initial network connection is no longer valid once the mobile device comes back into coverage, then the mobile device may send invalid or out-of-context queued data frames to the network. This situation may occur, for example, if the mobile device terminates the network connection while out of coverage. If invalid or out-of-context data frames are processed by the network, then synchronization may be lost between the mobile device and the network, resulting in an interruption in communication.